Listening-key circuits.



A. E. LUNDELL & F. A. STEARN.

LISTENING KEY CIRCUITS.

APPLICATION FILED ocnzs. ms.

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Patented Mar. 26,1918.

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ALDEN- E. LUN D ELL, 0F NE'MV YORK, 1\T. 1 AND FRANKLIN A. STEAR NEVIJERSEY, ASSIGNOBS TO "WESTERN ELECTRIC COMP Y., A ccEroEArIon or NEWYORK.

NEW YORK, n.

LISTENING-KEY CIRCUITS.

To all whom it may concern:

Be it known that we, Annex ll]. LUNDELL and FRANKLIN A. S'rEARN,citizens of the United States, residing, respectively, at New York, inthe county of Bronx and State of New York, and Paterson, in the countyof Passaic and State of New Jersey, have invented certain new and usefulImprovements in Listening-Key Circuits, of which the following is afull, clear, concise, and exact description.

This invention relates to telephone exchange systems employingoperators, and more particularlyto improvements in operatorslistening-key circuits.

It is the object of this invention to pro vide means whereby an operatormay listen from one cord to another at, a high rate of speed.

A feature of the invention is a double wound relay controlling a secondrelay, at whose contacts connection between its cord and the operatorshead-set may be made. When the operators head set is to be connected toanother cord, the high resistance locking circuit of the first relaywill be shunted out by the low resistance operating winding of thecorresponding relay associated with the second cord.

It is thought that the invention will be best understood from thefollowing detailed description, reference being had to the accompanyingdrawing.

In the drawing, the answering end of a connecting operators cord circuitis diagrammatically shown the right is shown a portion of the circuit ofa second cord at the same operators position.

Assuming that the position is idle and that a call comes in over theline terminat ing in jack 1, the operator will be informed in thewell-known manner by the lighting of the usual line lamp (not shown).She then inserts plug 2 into jack 1, whereupon a circuit will becompleted for relay 3, from ground, winding of relay 3, sleeve contactsof plug 2 and jack 1, to grounded battery through the winding of thewell-known cutoff relay (not shown). Relay 3, at its outer armature,completes a circuit from ground, outer armature and front contact ofrelay 3, left-hand armature and back contact of relay 4., left-handwinding of Specification of Letters Patent,

at the left, while at Serial No. 127,687.

ANY, IN

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Patented Mar. 26, 1918.

relay 5, armature and back contact of relay 6, and resistance 7 to Relayattracts its grounded battery.

urmatures, completing a circuit from ground, left-hand armature andfront contact of relay 5,

winding of relay 9 to grounded battery.

Relay 9 attracts lts armatures and completes a circuit from ground,

front contact of relay 9 power magnet 11 of sequence switch connectingat its right-hand armature connecting switch contact 10, right-hand cordsequence armature and w nding of the the connecting cord to groundedbattery. cord sequence switch The mo vcs from position 1 into position2, under the control of its normal spring 12.

In position 2 of the connecting cord sequence switch a circuit iscompleted from grounded battery, sequen ce switch contact 13, left-handarmature and front contact ground. Relay l relay 4:, right-hand tact ofrelay 4, inner armature andfront contact of relay 3 to grounded battery.

The operation of relay 4 allows a circuit,

previously shunted out contact, to completed battery,

through its back from grounded resistance 7, armature and back contactof relay 6, right and left-hand windings of relay 5 relay 8, right-handarmatl tact of relay 5 to ground.

in series, winding of ire and front con- Relays 5 and 8 are locked up inthis circuit.

As soon as relay 8 attr acts its armature,

the connecting operator may converse with the calling subscriber andascertain the number of the wanted line.

connections are desired,

If no further she listens-out by depressing listening-out key 14,whereupon relay 6 is energized and opens the en'- cuit through relayshead-set from the cord.

5 and S, whereupon they de'elnergize and disconnect the 'operatorsdepresslng the listening-0ut key, inserts a second plug into ananswering jack, the o 5 associated with such peration of relay secondcord Wlll shunt out relay 5, since the circuit through relay 5 is atthis time low-resistance left-hand w only through its inding. Relay 5,

upon actuation, locks itself to ground in a manner similar to that ofrelay 5, and ener- V with which such gizes a relay corresponding torelay 8 to connect the operator with the second cord.

Assuming now that the operator has listened-in on her second cord, andagain desires to listen-in on the first cord, she depresses listcning-inkey 15, whereupon a circuit will be closed from grounded battery,resistance 7 armature and back contact of relay 6, low-resistanceleft-hand winding of relay 5, armature and front contact of relay 4,which remains locked up as long as plug 2 remains in jack 1, to ground,through the contacts of key 15. The low resistance winding of relay 5 inturn shunts out the high resistance locking circuit through the twowindings of relay 5.

It is to be noted that only momentary depression of listening key 15 isrequired, since the relay 5 locks itself up as soon as it is actuated.

What is claimed is:

1. In a telephone exchange system, a plurality of subscribers lines, aplurality of link circuits for interconnecting'said lines, an operatorshead set, a plurality of relays, there being one of said relays per linkcircuit to control the connection of said head set to said linkcircuits, an energizing circuit completed for one of said relays asaresult of the extension of a line to the link circuit relay isassociated, means for denergizing said relay simultaneously with theenergization of a second one of said relays, and a manually operable keyto control the renergization of a previously actuated one of saidrelays.

2. In a telephone exchange system, a plurality of subscribers lines, aplurality of linkcircuits for interconnecting said lines, an operatorshead set, a plurality of relays, there being one per link circuit tocontrol the connection of said head set to said link circuits,energizing circuits for said relays, locking circuits for said relays,alternate means for completing said energizing circuits, and means forrendering a locking circuit ineffective whenever an energizing circuitis completed.

3. In a telephone exchange system, a plu rality of subscribers lines, aplurality of link circuits for interconnecting said lines, an operatorshead set, a plurality of double wound relays, there being one per linkcircuit, to control the connection of said head set to said linkcircuits, energizing circuits extending through one winding of saidrelays, locking circuits for said relays extend- Gopies of this patenting through both of their windings in series,

alternate means for completing said energizing circuits, and means forshunting out a locking circuit whenever circuit is completed. r

4. In a telephone exchange system, a plurality of subscribers lines, aplurality of link circuits for interconnecting said lines, an operatorshead set, a plurality of relays, there being one per link circuit tocontrol the connection of said head set to said'link circuits,energizing circuits for said relays, locking circuits for said relays,

a manually operable key, means for completing said enan energizingergizing circuits either upon momentary depression of said key or uponextension of a line to a link circuit, and means for rendering a lockingcircuit ineffective whenever an energizing circuit is completed.

5. In a telephone exchange system, a plurality of subscribers lines,.aplurality of link circuits for interconnecting said lines, a doublewound relay r'oreach of said link to establish connec- V circuits, asecond relay tion between said head set and its associated link circuit,and energizing circuit for said first relay extending through onewinding only, a locking circuit for said'first relay extending seriesand including the winding of second relay, a manually operablekey,

said and means to complete said energizing circuit to operation of saidkey-f either in response or in response to the extension of a callingline to a link ing out a locking circuit whenever an energizingcircuitis completed. 7 7 j V 6. In a telephone exchange'system, aplurality of subscribers lines, a plurality of link circuits forinterconnecting said lines, an operators head set, relays, one for eachlink circuit, to control the connection of said head set to said linkcircuits, energizing circuits for said relays, locking circuits forsaid'relays, a manually operable key incircuit, and means forshuntthrough its windings 111 dividual'to each of said link circuits,means for completing an energizing circuit for the relay of a linkcircuit either upon extension of a line to said link circuit or upondepression of the key corresponding to said link circuit, and means foropening any existing locking circuit whenever an energizing circuit iscompleted. 7 V

In witness whereof, we subscribe our names this 24th day of October, A.1)., 1916.

, ALBEN E. LUNDELL.

FRANKLIN A. STEARN.

may be obtained for five cents each, by addressing the"comniissioner ofPatents,

Washington, D. G.

